1. Field of the Invention
The present invention relates to a power management system, a power management method and a computer readable medium storing a program, allowing power management of a plurality of image forming apparatuses and, more specifically, to a scheme for power management considering degree of wearout among image forming apparatuses.
2. Description of the Related Art
With growing awareness of environmental issues, approaches have been made to reduce power consumption of various electric appliances. Such approaches are also made in the field of office equipment represented by an image forming apparatus.
It is often the case in an office to have a plurality of image forming apparatuses connected to a network including a plurality of personal computers. Schemes to reduce power consumption in such a system of network configuration have been proposed.
By way of example, Japanese Laid-Open Patent Publication No. 2002-351647 discloses a configuration in an image forming apparatus having a network function allowing connection to a plurality of external devices, for managing period setting before entering a sleep mode, depending on states of external devices connected to the network. Further, Japanese Laid-Open Patent Publication No. 2004-013203 discloses a network system optimally managing device power sources by estimating frequency of use of devices (image forming apparatuses) based on the number of boot-ups/accesses of clients under control of a server, in a network environment.
In the network system disclosed in Japanese Laid-Open Patent Publication No. 2004-013203, the server detects connected clients and assumes the number/type of necessary image forming apparatuses based on the total number of detected clients, and thereby selects an image forming apparatus from a group of image forming apparatuses controlled by the server and turns the power of the selected image forming apparatus ON or OFF.
In the network system, however, the image forming apparatus is selected based only on the past printing results of clients and a function table of image forming apparatuses and, therefore, frequency of selecting a specific image forming apparatus (for example, an image forming apparatus set at a higher position in the function table) comes to be relatively high, and operating ratio of the apparatus becomes higher than other apparatuses. As a result, degree of wearout varies among the group of image forming apparatuses.
If a specific image forming apparatus comes to have higher degree of wearout as described above, product life of the apparatus would be shorter than other apparatuses. As a result, efficient maintenance and management of the group of image forming apparatuses would be hindered, and required cost would be increased.